Transient gain analysis of gain-switched semiconductor lasers during pulse lasing

Abstract

We analyzed the transient gain properties of three gain-switched semiconductor lasers with different materials and cavity structures during pulse lasing. All the semiconductor lasers were pumped with impulse optical pumping, and all the generated gain-switched output pulses were well described by exponential functions in their rise parts, wherein the transient gains were derived according to the rate-equation theoretical model. In spite of the different laser structures and materials, the results consistently demonstrated that a higher transient gain produces shorter output pulses, indicating the dominant role of higher transient gain in the generation of even shorter gain-switched pulses with semiconductor lasers.

Subnanosecond Marx Generators for Picosecond Gain-Switched Laser Diodes

“…8(c) shows a log plot of the rising part of the waveform with a mono-exponential fitting. The constant rise time τrise = 7 ps obtained from the fitting result is a reflection of the saturation gain of the laser diode, which is a very important parameter that determines the gain-switching characteristics of the semiconductor laser diode [20,21] . According to the relationship between the rise time and the saturation gain [21], and considering the general structure of the laser diode, the saturation gain of the present laser diode is estimated to be in the order of 103 cm -1 , which is still lower than the theoretical maximum values in literatures [22], indicating that the pulse width can be further reduced by optimizing the laser structures.…”